Design, Synthesis and Study of Mechanical Properties of Crystalline Diphenyl Urea Derivatives

Deolka, Shubham (2017) Design, Synthesis and Study of Mechanical Properties of Crystalline Diphenyl Urea Derivatives. Masters thesis, Indian Institute of Science Education and Research Kolkata.

PDF (MS dissertation of Shubham Deolka (12MS064)) Shubham_Deolka-12MS064.pdf - Submitted Version Restricted to Repository staff only Download (2MB)

Abstract

Controlling mechanical properties of crystalline organic materials remains a forbidden challenge despite their wide range practical applications. Our group has recently demonstrated the importance of supramolecular shape synthons for designing mechanically flexible single crystals. Active slip planes were introduced in crystal structures via different non-interfering supramolecular weak interactions (shape synthons), namely via van der Waals (vdW), π- stacking, and hydrogen bonding (0D) (carboxylic acid or amide) groups. Here, we extend this design strategy to some diphenyl urea derivatives (as shown in figure 1), in which a linear one dimensional (1D) strong hydrogen-bonded chain is present in one direction which further stack one over the other. In the third orthogonal direction the molecule interact weak dispersive interactions (slip planes) in other direction, i.e, orthogonally. The two N-H groups of one molecule form hydrogen bonds with the C=O of an adjacent molecule, while the vdW substituents such as methyl, chloro and bromo groups on either ends of the phenyl rings close pack to form slip planes. Mechanical behavior of the crystals was examined by a simple qualitative method, i.e. applying mechanical stress using a pair of forceps and a metal needle while viewing them under a stereomicroscope. To our desire, the single crystals of 1 and 1a showed plastic flexibility on (1 0 0) and (1 0 0) respectively, while compound 2 underwent brittle fracture.

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